Carbon nanofibers derived from polymer nanofibers and method of producing the nanofibers

Abstract

A method for producing one or more nanofibers includes providing (a) a solution comprising a polymer and a solvent, (b) a nozzle for ejecting the solution, and (c) a stationary collector disposed a distance d apart from the nozzle. A voltage is applied between the nozzle and the stationary collector, and a jet of the solution is ejected from the nozzle toward the stationary collector. An electric field intensity of between about 0.5 and about 2.0 kV/cm is maintained, where the electric field intensity is defined as a ratio of the voltage to the distance d. At least a portion of the solvent from the stream is evaporated, and one or more polymer nanofibers are deposited on the stationary collector as the stream impinges thereupon. Each polymer nanofiber has an average diameter of about 500 nm or less and may serve as a precursor for carbon fiber production.

The invention claimed is: 
     
       1. A method of producing one or more nanofibers, the method comprising:
 providing (a) a solution comprising a polymer and a solvent, (b) a nozzle for ejecting the solution, and (c) a stationary collector disposed a distance d apart from the nozzle; 
 applying a voltage between the nozzle and the stationary collector; 
 ejecting a jet of the solution from the nozzle toward the stationary collector; 
 maintaining an electric field intensity between about 0.5 and about 2.0 kV/cm as the jet is ejected, the electric field intensity being defined as a ratio of the voltage to the distance d; 
 evaporating at least a portion of the solvent from the jet; 
 depositing one or more polymer nanofibers on the stationary collector as the jet impinges thereupon, each polymer nanofiber having an average diameter of about 500 nm or less; 
 after the depositing, cold drawing the one or more polymer nanofibers at a strain rate between about 10 −4  s −1  and 200 s −1 ; and 
 after the cold drawing, forming carbon nanofibers from the one or more polymer nanofibers. 
 
     
     
       2. The method of  claim 1 , wherein the distance d is at least about 25 cm. 
     
     
       3. The method of  claim 1 , wherein the distance d is about 20 cm or less. 
     
     
       4. The method of  claim 1 , wherein the electric field intensity is between about 1.3 kV/cm and about 1.7 kV/cm. 
     
     
       5. The method of  claim 1 , wherein the electric field intensity is between about 0.8 kV/cm and about 1.2 kV/cm. 
     
     
       6. The method of  claim 1 , wherein the cold drawing is carried out at a strain rate between about 2.5×10 −2  s −1  and about 100 s −1 . 
     
     
       7. The method of  claim 1 , wherein forming the carbon nanofibers comprises:
 stabilizing the one or more polymer nanofibers by heating at a temperature of at least about 300° C. for 1 hour, thereby forming one or more stabilized nanofibers; and 
 carbonizing the one or more stabilized nanofibers to form the carbon nanofibers, the carbonizing comprising heating the stabilized nanofibers at a temperature between about 1400° C. and about 1700° C. 
 
     
     
       8. The method of  claim 1 , wherein the stationary collector comprises a plurality of parallel metal wires. 
     
     
       9. The method of  claim 1 , wherein the stationary collector is grounded.